title: Plasmid-encoded proinsulin preserves C-peptide while specifically reducing proinsulin-specific CD8⁺ T cells in type 1 diabetes.
abstract: In type 1 diabetes (T1D), there is an intense inflammatory response that destroys the β cells in the pancreatic islets of Langerhans, the site where insulin is produced and released. A therapy for T1D that targets the specific autoimmune response in this disease while leaving the remainder of the immune system intact, has long been sought. Proinsulin is a major target of the adaptive immune response in T1D. We hypothesized that an engineered DNA plasmid encoding proinsulin (BHT-3021) would preserve β cell function in T1D patients through reduction of insulin-specific CD8⁺ T cells. We studied 80 subjects over 18 years of age who were diagnosed with T1D within the past 5 years. Subjects were randomized 2:1 to receive intramuscular injections of BHT-3021 or BHT-placebo, weekly for 12 weeks, and then monitored for safety and immune responses in a blinded fashion. Four dose levels of BHT-3021 were evaluated: 0.3, 1.0, 3.0, and 6.0 mg. C-peptide was used both as an exploratory efficacy measure and as a safety measure. Islet-specific CD8⁺ T cell frequencies were assessed with multimers of monomeric human leukocyte antigen class I molecules loaded with peptides from pancreatic and unrelated antigens. No serious adverse events related to BHT-3021 were observed. C-peptide levels improved relative to placebo at all doses, at 1 mg at the 15-week time point (+19.5% BHT-3021 versus -8.8% BHT-placebo, P < 0.026). Proinsulin-reactive CD8⁺ T cells, but not T cells against unrelated islet or foreign molecules, declined in the BHT-3021 arm (P < 0.006). No significant changes were noted in interferon-γ, interleukin-4 (IL-4), or IL-10 production in CD4 T cells. Thus, we demonstrate that a plasmid encoding proinsulin reduces the frequency of CD8⁺ T cells reactive to proinsulin while preserving C-peptide over the course of dosing.
authors.affiliation: Department for Immunohematology and Blood Transfusion, Leiden University Medical Center, 2333 ZA Leiden, the Netherlands.
authors.forename: Bart O
authors.initials: BO
authors.lastname: Roep
authors.affiliation: Bayhill Therapeutics, Palo Alto, CA 94304, USA.|Foothill College, Los Altos, CA 94022, USA.
authors.forename: Nanette
authors.initials: N
authors.lastname: Solvason
authors.affiliation: Barbara Davis Center for Childhood Diabetes, Aurora, CO 80045-6511, USA.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Gottlieb
authors.affiliation: Department for Immunohematology and Blood Transfusion, Leiden University Medical Center, 2333 ZA Leiden, the Netherlands.
authors.forename: Joana R F
authors.initials: JRF
authors.lastname: Abreu
authors.affiliation: Division of Molecular Medicine, Walter and Eliza Hall Institute for Medical Research, Parkville, Victoria 3052, Australia.
authors.forename: Leonard C
authors.initials: LC
authors.lastname: Harrison
authors.affiliation: Barbara Davis Center for Childhood Diabetes, Aurora, CO 80045-6511, USA.
authors.forename: George S
authors.initials: GS
authors.lastname: Eisenbarth
authors.affiliation: Barbara Davis Center for Childhood Diabetes, Aurora, CO 80045-6511, USA.
authors.forename: Liping
authors.initials: L
authors.lastname: Yu
authors.affiliation: Bayhill Therapeutics, Palo Alto, CA 94304, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Leviten
authors.affiliation: Pacific Northwest Diabetes Research Institute and University of Washington, Seattle, WA 98122, USA.
authors.forename: William A
authors.initials: WA
authors.lastname: Hagopian
authors.affiliation: Diabetes Center for Research, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: John B
authors.initials: JB
authors.lastname: Buse
authors.affiliation: La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA.
authors.forename: Matthias
authors.initials: M
authors.lastname: von Herrath
authors.affiliation: Bayhill Therapeutics, Palo Alto, CA 94304, USA.
authors.forename: Joanne
authors.initials: J
authors.lastname: Quan
authors.affiliation: Bayhill Therapeutics, Palo Alto, CA 94304, USA.
authors.forename: Robert S
authors.initials: RS
authors.lastname: King
authors.affiliation: Bayhill Therapeutics, Palo Alto, CA 94304, USA.|Departments of Medicine and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA.|Tolerion Inc., 321 Dedalera Drive, Portola Valley, CA 94028, USA.
authors.forename: William H
authors.initials: WH
authors.lastname: Robinson
authors.affiliation: Bayhill Therapeutics, Palo Alto, CA 94304, USA.|Departments of Medicine and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA.|Tolerion Inc., 321 Dedalera Drive, Portola Valley, CA 94028, USA.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Utz
authors.affiliation: Bayhill Therapeutics, Palo Alto, CA 94304, USA.|Tolerion Inc., 321 Dedalera Drive, Portola Valley, CA 94028, USA.
authors.forename: Hideki
authors.initials: H
authors.lastname: Garren
authors.affiliation: Bayhill Therapeutics, Palo Alto, CA 94304, USA.|Departments of Medicine and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA.|Tolerion Inc., 321 Dedalera Drive, Portola Valley, CA 94028, USA.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Steinman
mesh_terms: D000328:Adult; D002096:C-Peptide / Q000378:metabolism*; D018414:CD8-Positive T-Lymphocytes / Q000382:microbiology*; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology* / Q000628:therapy*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D010957:Plasmids / Q000235:genetics*; D011384:Proinsulin / Q000235:genetics / Q000378:metabolism*
chemical_list: D002096:C-Peptide; D011384:Proinsulin